CRITICAL CONSIDERATIONS 7 in the observation of nature, and have raised them to the level of those zoologists who get up in the middle of the night to make tiresome journeys into the woods that they may be present at the Awakening and the first doings in the daily life of some family of insects in which they are interested. Here we have the scientist who may be sleepy or weary of the way, but who is yet unrelaxing in his vigilance; he is not aware that he is muddy or dusty, he does not mind when the mists are soaking him or the sun is scorching him; he is intent solely on keeping his presence a dead secret, that, hour after hour, the insects may quietly perform their natural functions which he is keen to observe. Let us suppose that they have reached the stage of that scien- tist who, already short-sighted, knowing how the work will tire his eyes, yet keeps under observation under the microscope the natural movements of some infusoria. He comes to the conclusion that in their mode of separating from one another and of select- ing food they are endowed with a shadowy consciousness or instinct. He then disturbs this quiet life of theirs with an electric stimulus, noticing how some group themselves round the positive pole and some round the negative. Then he experiments with light stimulus and watches how some hasten towards the light whilst others avoid it. In this way he studies the phenomena of tropism, always keeping in the forefront the thought that what has to be decided is whether or not the attraction to or the avoidance of stimuli is of the same character as that of the natural separations and the choice of food; in other words, he wants to know if the movements are prompted by choice and a dawning conscious- ness, or better by natural instinct, rather than by some physical attraction and repulsion like that which exists between a magnet and iron. And let us suppose that this scientist, finding that it is two o'clock in the afternoon and that he has not yet had his lunch, is delighted to think that he has been working in a labo- ratory instead of in his home, where he would have been called two hours before and interrupted both in his interesting obser- vations and in his fast.